The present invention relates to an adjunct interface module which is typically used to connect adjunct telephone equipment to a telephone switching system.
An on-premise switching system, such as a private branch exchange (PBX) or a key/hybrid telephone system, typically provides an on-premise user with access to a set of telecommunication features through a nonstandard telephone set. The telephone set is nonstandard in that it is designed to connect to the telephone set interface provided by the on-premise switching system. The telephone set interface provided by the on-premise switching system can either have more conductors, different line voltages, and/or different signaling rates than a common telephone loop, or "tip-ring", interface provided by a central office. As a result of this different telephone set interface, the switching system is able to offer a set of features to the user at a better price/performance ratio than might be available with conventional, tip-ring telephone equipment.
However, a user may have an investment in adjunct telephone set equipment that is built with the tip-ring telephone interface, e.g., a telephone answering machine, or built with yet another interface, such as an external alert interface. This adjunct equipment may offer the user services that may not yet be available, or affordable, in the user's premise switching system. As a consequence, for the user who would still like to use adjunct telephone equipment, on-premise switching vendors typically provide a physically separate adjunct interface module to the user to convert the adjunct telephone equipment interface to the telephone set interface of the premise switching system.